class Container {
  static of (value){
    return new Container(value)
  }
  constructor(value){
    this._value = value
  }
  map(fn){
    return Container.of(fn(this._value))
  }
}

class Maybe {
  static of (value){
    return new Maybe(value)
  }
  isNothing(){
    return this._value === null || this._value === undefined
  }
  constructor(x){
    this._value = x
  }
  map (fn){
    return this.isNothing() ? this : Maybe.of (fn(this._value))
  }
}

module.exports = {Maybe, Container}